1. Field of the Invention
This invention relates generally to environmentally stable optical filter materials and, in particular, to polymers which may be used as optical-filter media on semiconductor devices for the transfer and printing of color images. The optical filter materials are highly temperature stable and incorporate chromophores yielding a variety of colors which can be used in combination to create colored patterns. The polymers may also be used as antireflective layers in the fabrication of semiconductor devices using photolithography.
2. Description of Related Art
Optical-filter media such as dyed gelatin or resist layers are used as layers on semiconductor devices for the transfer and printing of color images. Typically, photoresists, containing labile dye compounds, are imaged to form colored patterns over a semiconductor substrate. These layers filter optical energy to the semiconductor surface, such as a charge coupled device; however, the layers lack a robust character and degrade on environmental exposure. Furthermore, manufacture of such devices with resist films require long bake times and frequently encounter solvent incompatibilities between overlying or underlying layers of resists in laminated structures. Additionally, resist striations can occur which impede uniformity of the product film.
A number of patents have issued using color filters with charge coupled devices and other devices in solid state color cameras, film video players, signal processing systems and the like. Exemplary U.S. patents in which the present invention are useful include U.S. Pat. Nos. 4,054,906; 4,059,839; 4,495,516; 4,663,656; and 4,985,758, the disclosures of which are incorporated herein by reference.
In the fabrication of integrated circuits, a photosensitive polymer film is applied to the silicon wafer, dried, and then exposed through a photomask to ultraviolet light or other radiation with the proper geometrical patterns. After exposure, the wafer is soaked in a solution that develops the images in the photosensitive material. Depending upon the type of polymer used, either exposed or nonexposed areas of the film are removed in the developing process.
A frequent problem encountered in such photolithographic processes to fabricate semiconductor devices is reflectivity back into the resist of the activating radiation by the substrate, especially those containing highly reflecting topographies. Such reflectivity tends to cause standing wave ripples and reflective notches which interfere with the desired pattern in the photoresist. To minimize this problem, chromophores have been introduced into the photoresist materials or in the underlying layers so that the photoresist or the underlying layer absorbs additional radiation upon exposure during the patterning process. Polyimides have been used with chromophores to provide such an antireflective underlying layer.
It is also common knowledge in the art to apply a photoresist layer over a polyamic acid film layer, expose the films to actinic radiation through an image defining mask, and simultaneously develop and etch the films in a basic aqueous solution to create an image in the amic acid film.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an optically sensitive, preferably high temperature resistant, polymer which may be used as an optical-filter media on semiconductor chips and other substrates and in the fabrication of integrated circuit devices.
It is a further object of the present invention to provide a composition of matter which is curable to form an environmentally stable highly temperature resistant optical filter polymeric film.
It is another object of the present invention to provide a method for the fabrication of semiconductor chips, optical-filter media or other substrates requiring a highly temperature stable film which absorbs light radiation.
Other objects and advantages of the present invention will in part be obvious and will in part be apparent from the specification.